17-β-Hydroxysteroid dehydrogenase III deficiency is clinically characterized by either ambiguous external genitalia or complete female external genitalia at birth; as a consequence of impaired male sexual differentiation in 46,XY individuals. Further investigations on ambiguous genitalia will eventually lead to findings of intersexuality. Severely impaired virilization (often complete absence of male sexual differentiation) can lead to development of female external genitalia. These children are raised as female, and their diagnosis is often discovered when there is absence of menarche (first menstruation) and when they begin to virilize during puberty (slowly become more like a man; deepening of the voice, acne, male musculature etc.). At careful examination, testis can often be found in the inguinal channel.
Biochemical effects of 17β-hydroxysteroid deficiency-3 in testosterone biosynthesis. Typically levels of androstenedione are significantly increased, whilst testosterone levels are decreased, leading to male undervirilization.
17β-Hydroxysteroid dehydrogenase III deficiency is characterized biochemically by decreased levels of testosterone and increased levels of androstenedione as a result of the defect in conversion of androstenedione into testosterone. This leads to clinically important higher ratio of androstenedione to testosterone (A'dion/T) (see figure).
^Boehmer, A. L. M. (1999). "17 -Hydroxysteroid Dehydrogenase-3 Deficiency: Diagnosis, Phenotypic Variability, Population Genetics, and Worldwide Distribution of Ancient and de Novo Mutations". Journal of Clinical Endocrinology & Metabolism84 (12): 4713–21. doi:10.1210/jc.84.12.4713. PMID10599740.